Segregation apparatus

ABSTRACT

In the process of U.S. Pat. No. 3,300,299, material in the chamber through which continuous plug flow takes place is caused to oscillate in level, in response to pressure probe measurements, either by intermittently discharging from the chamber or by varying the rate of discharge between a level which is higher than the rate of inflow into the chamber and a level which is lower than that rate of inflow.

Unite States Moore Mar. 27, 1973 54] SEGREGATION APPARATUS 2,331,505 8/1945 Lindholm ..222/64 [75] Inventor: Victor J. Moore, Nkana East, Zam- 3'588521 6/1971 Stone 222/64 R f S 3,430,814 3 1969 Cymbahsty... ..222 64 0 out 3,114,479 12 1963 Keeney ..2 22/64 [73] Assignee: Anglo American Corporation of 3,627,555 12/1971 Dlfiscon-w 222/64 South Africa Limited, Johan- E A veson nesburg Repubhc of South fnca 2,742,353 4 1956 Ogorzaly ..75/26 [22] Filed: May 14, 1970 2,561,396 7/1951 Matheson ..75/26 2,560,175 7/1951 Kalbach ..75/26 [21] 37,336 3,022,156 2/1962 Eastman... ..75 26 3,129,849 4/1964 Cochran... .....222/64 Related Appl'cafion Dam 3,227,546 1 1966 Johnson ..75/26 [62] Division of Ser. No. 670,620, Sept. 26, 1967, abandoned- Primary Examiner-L. Dewayne Rutledge Assistant Examiner-Peter D. Rosenberg Foreign Alllllifiition l' Dam Attorney-Young and Thompson Sept. 28, 1966 South Africa ..L66/5859 [57] ABSTRACT [52] U.S. Cl. ..266/20, 75/26, 75/34, In the recess of us. Pat 3,300,299 material in l the chamber through which continuous plug flow [51] z 21/00 g 3 3? takes place is caused to oscillate in level, in response [58] F e d 0 "75/2 3 g: to pressure probe measurements, either by intermittently discharging from the chamber or by varying the rate of discharge between a level which is higher than [56] Rderences Cited the rate of inflow into the chamber and a level which UNITED STATES T S is lower than that rate Of inflow.

3,300,091 1/1967 Wondrak.....' ..222/64 1 Claim, 4 Drawing Figures PATENTEUMARN 1975 sum 10F 2 Mum me w M wfl Ma r 2/ mm w? SEGREGAT'ION APPARATUS The present application is a division of copending application Ser. No. 670,620, filed Sept. 26, 1967, and now abandoned.

This invention relates to improvements in segrega tion apparatus.

Segregation of particulate materials has been known for many years in connection with the recovery of copper. It has now been demonstrated that metals other than copper can also be caused to segregate by a choice of suitable conditions. The present invention is applicable to the segregation process regardless of the metal to which it is applied.

The present applicant has already in the specification of US. Pat. No. 3,300,299 proposed a modification of the segregation process which, it is believed, will make the process commercially more viable than other ways of carrying out the segregation process. However, in scaling ,up the procedures taught by the prior proposal, certain difficulties were encountered. Most of these difficulties were expected and of a mechanical nature, but for some reason, which even now is not clear, the degree of segregation was not consistent and did not come up to the high level found in pilot plant operations.

Basically in the previously proposed modification an ore is heated in a fludized bed and then caused to flow from the bed in the form of a plug, reagents necessary for the segregation reaction being added to the plug. It is inherent for the success of the process that there be true plug flow. Usually plug flow is achieved by causing the heated ore to flow in a vertical column and the discharge from the column is controlled by some form of continuous discharge valve. In practice star valves have been found to be suitable.

A new type of sleeve valve has also been found to be satisfactory for achieving continuous discharge.

In an attempt to ensure true plug flow, rodding of the chamber was resorted to and a baffle system was built into the base of the chamber to ensure that all particles descending down the chamber followed the same path length. But still the segregation results proved to be erratic and on average below what was expected. After months of operation, the best that was achieved was 80 percent segregation during some-runs. Even then the very next day, under apparently identical conditions, and with apparently the same ore, the percentage segregation would drop off, sometimes to as low as 50 percent.

It has now unexpectedly been found that if the level of solids in the chamber is caused to oscillate between predetermined levels, segregation rates of up to 100' percent may be achieved. No logical explanation for this phenomenon has yet been advanced.

In a process in which an ore containing a metal amenable to segregation is heated in a fluidized bed and then caused to flow from the bed in the form of a plug through a segregation chamber and the reagents necessary for segregation are added to the chamber, the invention provides the improvement of causing the level of the solids in the chamber to oscillate between predetermined levels.

Oscillation may be achieved by regulating the discharge from the chamber. Thus the rate of discharge may be varied between a low value (which may be zero) lower than the rate of feed to the chamber and a high value higher than the rate of feed to the chamber.

The invention is further discussed with reference to the accompanying drawings, in which FIG. 1 is a diagrammatic section through an installation operating on the principles disclosed in the above identified patent application, now abandoned.

FIG. 2 is a side view of part of FIG. 1,

FIG. 3 is a view similar to FIG. 2 of a variation of the invention, and

FIG. 4 is again a view similar to FIG. 2 of another variation.

In FIG. 1 ore is fed to a fluidized reactor bed 3 and overflows over a lip 2 into a segregation chamber 4. Solids entrained by the fluidizing gas are recovered in cyclones 5 and 6 and returned to the chamber 4. Reagents, coal and salt, are added to the chamber 4 through the down leg of the cyclone 6.

1 The chamber 4 is a vertical cylindrical vessel having an inverted conical base 7 terminating in a star valve 8. Above the valve 8 there may be a system of baffles 9.

The valve 8 discharges into a quench tank (not shown) and the product is treated for the recovery of segregated metal in any suitable way, e.g., by flotation.

If the plant described is run with a given ore, at a given reagent feed rate and at a given temperature with the rate of feed to the chamber 4 equal to the rate of discharge through the valve 8, segregation is disappointingly low and erratic. Under the best conditions a conversion of copper minerals to metallic copper of between 70 and 80 percent can be achieved.

The modifications brought about by the present invention are more fully illustrated in FIG. 2. In this Figure there are two pressure probes l0 and 11 (also seen in FIG. 1) spaced apart at a suitable distance. The

outputs of the probes l0 and 11 are fed to a control device 12 which in turn controls a magnetic clutch 13 which drives the valve 8 through a shaft 17. The clutch 13 is driven from a motor 14 through a suitable gear box 15.

The control device 12 is arranged to energize the clutch 13 when a signal from the probe 10 indicates the presence of material at the level of the probe. Thus the valve 8 will rotate and discharge material from the chamber 4. As soon as a signal from the probe 11 indicates the absence of material at the level of the probe 11, the clutch is de-energized and the valve 8 stops rotation.

In experiments with an installation according to FIG. 2 and in all other examples quoted in this specification an attempt was made to cause the level in the chamber to oscillate between levels'which differed by about 60 In one example making use of the installation of FIG.

' 2 the valve 8 was run at 18 r.p.m., was stopped for 60 respect to the signals from the pressure probes 10 and An alternative to FIG. 2 is illustrated in FIG. 3. In

this case the probes 10 and 11 feed signals to a control device 12 which controls a speed control device 16 which controls the the motor 14 between two alternate speeds. If the probe signals the presence of material at its level, the speed of the motor 14 is set at the higher of the two alternate speeds. As soon as the probe 11 signals the absence of material at its level, the motor 14 is switched to the lower speed.

The higher speed is chosen to cause the valve 8 to discharge material faster than the rate of overflow from the reactor bed 3 and the lower speed to discharge material slower than the overflow.

Conversions of over 95 percent were obtained where the speed of the valve 8 was 18 rpm. at the higher speed and 9 rpm. at the slower speed.

In the embodiment of FIG. 4 discharge from the chamber 4 was achieved by means ofa sleeve valve 18.

The valve 18 is caused to open and close by a double acting pneumatic cylinder 20, acting on a lever 19 connected to the valve 18. In this case the control device 12 opens and closes valves 21 and 22. If the probe it) signals the presence of material the valve 21 is opened and the lever 19 is pushed to open the valve 18. At the same time the valve 22 is set to exhaust air from the other side of the cylinder 20. A signal from the probe 11 that material is absent at its level causes the valve 21 to be turned to exhaust and the valve 22 to be turned on for the lever 19 to be pushed in a direction causing the valve 18 to close.

In operation with the embodiment of FIG. 4 the valve 18 has always been caused to close entirely when the probe 11 gave its signal. In the event segregation percentages of 95 percent and better were obtained. It is, of course, possible to move the valve 18 to close only to an extent necessary to cause the rate of discharge to be lower than the rate of overflow into the chamber 4.

In the operations referred to the cylinder performed 35 to 40 strokes per hour and on average the valve 18 was open for about 12 seconds and closed for about seconds at a time.

Having described my invention, I claim:

1. In apparatus for the segregation of particulate material, comprising a fluidized bed heater, a segregation chamber into which heated material overflows from the fluidized bed, a discharge at the foot of the chamber and means to feed reagents to the chamber; the improvement comprising a discharge valve at the foot of the chamber adapted to operate so as to vary the rate of discharge between a first rate that is higher than the rate of overflow into the chamber and a second rate which is lower than the rate of overflow, a first detector at a high level in the chamber for detecting the presence of material at that level, a second detector at a low level in the chamber of detecting the absence of material at that level, and control means responsive to the detectors arranged to control the operation of the discharge valve, the control means being responsive to the first detector to cause the valve to cause discharge at the first rate and being responsive to the second detector to cause the valve to cause discharge at the second rate. 

1. In apparatus for the segregation of particulate material, comprising a fluidized bed heater, a segregation chamber into which heated material overflows from the fluidized bed, a discharge at the foot of the chamber and means to feed reagents to the chamber; the improvement comprising a discharge valve at the foot of the chamber adapted to operate so as to vary the rate of discharge between a first rate that is higher than the rate of overflow into the chamber and a second rate which is lower than the rate of overflow, a first detector at a high level in the chamber for detecting the presence of material at that level, a second detector at a low level in the chamber of detecting the absence of material at that level, and control means responsive to the detectors arranged to control the operation of the discharge valve, the control means being responsive to the first detector to cause the valve to cause discharge at the first rate and being responsive to the second detector to cause the valve to cause discharge at the second rate. 